Making nitro compounds.



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CAREETON ELLIS AND ALFRED A. WELLS, OF MONTCLAIR, NEW JERSEY, ASSIGNOBS T0 ELLIS-FOSTER 00., A CORPORATION OF NEW JERSEY.

MAKING NITRO COMPOUNDS.

No Drawing.

To all whom it may concern.

Be it known that we, CARLn'roN ELLis and ALFRED A. VVnLLs, citizens. of the United States, and residents of Montclair, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Making Nitro Compounds, of which the following is a specification.

This invention relates to the preparation of nitro aromatic bodies such as the nitro derivatives of ben zol and the like and relates particularly to the production of nitrophenols suitable for use in the manufacture of picric acid and sulfur black.- The invention will be illustrated with respect to the preparation of dinitrochlorbenzol and th corresponding dinitrophenol.

Picric acid is usually manufactured from i carbolic acid, which may be obtained in a state'of comparative purity-and the picric acid obtained thereby if carefully prepared is almost chemically pure. The specifications of the Various governments for picnic acid to be used as an explosive are very rigid, calling for a product of the utmost purity.

Numerous attempts have been made to prepare picric acid from sources other than carbolic acid but most of these do not give a product answering to the requirements of a high explosive. For example, the melting point may be too low or the ash content too high or the product discolors on heating or contains free acid and the like. By the present process it is possible to obtain for example, dinitrophenol in such a state of purity that picric acid may be prepared therefrom by furthernitration, which product possesses the properties required.

- In carrying out the present process, illustratively, the prepared raw material is chlorbenzol and in preparing this product by the chlorination of benzol a certain amount of dichlorbenzol and other bodies are obtained Whichare somewhat troublesome to completely eliminate from the chlorbenzol. The latter also may contain a trace of benzol, toluol, xylol, and the like, if not carefully prepared. These impurities appear at a later stage to militate against the purity of the resulting product, and oftentimes are Specification of Letters Patent.

as mononitrochlor and dinitrochlorbenzol by the action of nitric acid liberated from so- -.dium nitrate or equivalent nitrate by the action of a compatible acid suclras sulfuric acid, in part at least in the presence of chlorbenzol so that a condition of nascency is secured and a part at least of the freshly liberated nitric acid is caused, or allowed, to react withthe chlorbenzol under condi-' tions to form the mono or dinitrochlorben- 201 to especially good advantage and with suitable heating or cooling as the case may be to maintain a temperature such that the liberation of nitric acid progresses smoothly and the nitration of the chlorbenzol progresses in a controllable manner thereby minimizing the formation of impurities, byproducts such as tars and resins and diminishing the dangerof explosions such as may occur when large quantities of mixed nitric and sulfuric acid are allowed to react on such raw materials. \Vhether the satisfactory result obtained in the present intention is directly due to the condition of nascency of the nitric acid or to its preparation, in situ, or whether the gradual formation of the nitric acid under preferred conditions of operation is conducive to a more controllable reaction within the limits desired, is diflicult to state and it may be possible that both of these factors are active in the satisfactory progress of the reaction.

The process also makes it possibleto use sulfuric acid of a comparatively low grade such as 66 B. acid instead of 96% or fuming sulfuric acid which are more costly and also avoids the shipment of liquid nitric acid, as the nitrating material is employed in the form of a dry salt.

In chlorinating benzol, as stated, it is not H Patented Mar. 20, 1917.

' Application filed May 31, 1916. Serial No. 100,776.

always possible to secure the monochlorv na'rily has a low melting point or in other and the like may formed, especially ifgreat care is not taken in every stage of the operation. Hence the conversion of material prepared in this manner into dinitrophenol and subsequent transformation into picric acid yields a product which'ordirespects does not resp'ondtothe official tests.

In' the present process when directed to the production of dinitrophenol and picric acid,

means are provided as'stated, for eliminating at one or more stages of the operation all or substantially all of these impurities,

' method of procedure so ofmonochlorbenzol isthen added slowly,

enabling a product be prepared.

The following serves as an illustrative About 2 parts by weightof sodium nitrate (crystals) and 6 parts of sulfuric acid of 66 Ba are placed in a nitrating kettle equipped with amechanical stirrer and with heating and cooling coils orjackets and are agitated until the sodium nitrate is practically all. in solution. In some cases this mix may be separately prepared. 7 1 part or while the mixture is cooled, the temperature not being allowed to rise above 100 C. After the chlorbenzol has'all been added the temperature is maintained at about 100 C: for several hours and it. is then gradually raiseduntil at the end of say about 15 hours nitration, the temperature has reached preferably about 125 C. Nitration is carried on at this temperature until the nitration is complete which will require about 24 hours.

During this operation the control of temperature maybebest observed by. watching the yellowish to reddish fumes given off from the 'nitrating mixture.- If properly conducted, at no time should there be a copious evolution of nitric or other nitrogen oxid fumes as this means a loss'of nitric acid. A vent pipe from the nitrating kettle may be "fitted with a sight glass to determine the depth of color of the fumes. If of a deep red color and copious in amount the reactionis progressing too violently for best results and economy of acidL; When the operation' is complete the contents of the nitrati'ng kettle are allowed to stand for a short while untilthey have separated in' two molten or liquid layers. The top layer consists of the nitrated bodies while the lower layer consists of a mixture of sodium sulfate,

sulfuric acid and a small amount of nitric acid. The lower layer may be drawn off and is valuable in many technical operations for its acid content. The top layer is then drawn-off into another vessel where it is treated with water toremove freeacid and the dinitrochlorbenzol thus obtained is suitably collected. Or the layer of nitrated bodies may be hydrolyzed with approximately a 10 per cent. solution of caustic of excellent quality to soda whichremoves the combined chlorin and produces the'sodium salt of dinitrophenol. If this operation is carried on in too concentrated solutions the sodium phenate will crystallize out which-is preferably to be avoided. Thev -'alkaline' solution is boiled without pressure for about two hours which-usually will suflice to completely convert the dinitrochlorbenzol into sodium dinitrophenate, without affecting mononitrochlorbenzol. Live steam is then turned into the boiling mixture and the whole mass thoroughly steamed, as long as any oily bodies come over as may be shown by a condenser attached to the receptacle. When oily particles cease to be discharged therefrom, this. purification step is completed.

The steaming operation serves to eliminate bodies such as mononitrochlorbenzol, etc.

' Any tarry material or heavier oils which are not soluble in the alkaline solution, or

removable by steaming, may be drawn. off from the bottom of the hydrolyzing tank, thus further purifying the product. The remaining portion of the alkaline solution is drawn off to be acidified. The ordinary procedure of acidification is to pour the diluted acid into the sodium salt, but a purer product is better obtained by reversing this operation and running the sodium salt into dilute acid. This product is readily filtered on a .cloth strainer and may be readily washed and dried by pressing in a bag press. For ordinary operations it is not essential .to thoroughly dry the material before converting either into 'picric acid or into a dye stufi such as sulfur black although in the former case a saving in the amount of acid is secured. Thus'according to the present invention, the preparation of dinitrophenol of high purity may be accomplished by' the use of. sodium nitrate as a source of nitric acid in the nitration, by the control of temperature in such a manner as to make economic use of the materials used and to regu-' late the rate and degree of nitration and by the purification of sodium dinitrophenate by distilling with steam and drawing ofl any alkali insoluble material while working in such dilutions as to keep the sodium salt always in solution. -With no purification steps other than those stated above it is possible to obtain dinitrophenol which is practically pure having substantially the correct melting point and possessing a good with sodium nitrate or equivalent nitrate and with a compatible acid capable of lib-' crating nitric acid preferably sulfuric acid and heat-ing'to a temperature at which nitration progresses preferably smoothly and regularly and without violent reaction and evolution of large quantities of oxids of nitrogen but proceeding instead in a controlled manner; whereby nitric acid .isliberated more or less regularly from the sodium nitrate and is in like manner united with the chlorbenzol forming the nitrochlorbenzols, preferably the dinitrochlor com-' pound, with scarcely any loss of nitric acid; thereby enablingapproximately equivalent proportions of chlorbenzol and sodium nitrate to be employed in an advantageous and economical manner. And the invention further comprises the step of forming nitrophenols, preferably a compound such as dinitrophenol, in a substantially pureccondition, as by incorporating crude dinitrochlorbenzol with aqueous alkali such as dilute caustic soda solution and in heating without pressure or otherwise under conditions which substantially avoid the hydrolysis of mononitrochlorbenzol, to remove the chlorin from the dinitro compound and substitute the hydroxyl group thereby yielding dinitrophenol in solution in the formof the sodium salt, and in separating any mononitrochlorbenzol from the sodium salt by steaming settling and the like; whereupon the substantially pure sodium salt may be acidified to liberate the dinitrophenol. which acidification step is preferably carried out by adding the sodium salt solution to an'excess of acid rather than adding acid to the sodium salt solution, since by the former procedure a product of lighter color is more likely to be obtained. The invention further contemplates the nitration. of the dinitrophenol under suitable nitrating conditions to form picric acid of satisfactory purity. hat we claim is 1. In the process of making nitro derivatives of benzol, the step which comprises heating a mixture comprising chlorbenzol sodium nitrate and sulfuric acid to a tem- I perture at which nitration progresses regularly but at which no copious evolution of oxid of nitrogen fumes occurs. r

2. In the process of making nitro derivatives of benzol, the step which comprises heating a mixture comprising chlorbenzol,

- alikali nitrate and sulfuric acid to a temperature at which nitration progresses regularly but at which no copious evolution of Ted fumes occurs.

3. In the process of making nitro derivatives of benzol, the step which comprises heating a mixture of chlorbenzol, sodium nitrate and 66 B. sulfuric acid to a temperature at which nitration progresses regularly but at which no copious evolution of red fumes occurs.

l. In the process of making derivatives of benzol, the step of nitrating chlorbenzol which comprises heating chlorbenzol, sodium nitrate and 66 B. sulfuric acid and nitric acid comprising nascent nitric acid to a temperature at which nitration progresses regularly without evolution of large quantities of oxids of nitrogen.

5. Inthe process of making derivatives of benzol, the step of nitrating chlorbenzol which comprises heating chlorbenzol with freshly-prepared nitric acid containing at least some portion thereof in a condition of n'a'scencyj 6. In the process of making nitro derivatives of benzol, the step of making dinitrochlorbenzol which comprises heating chlorbenzol, sodium nitrate and sulfuric acid to a temperature in the neighborhood of but substantially not exceeding 130 C.

tions to yield only a slight excess of nitric acid and in controlling the rate of formation of the nitric acid and in regulating the temperature in such a manner that substantially no nitric acid is lost.

10. In the process of making derivatives of benzol, the step of making dinitrochlorbenzol which comprises heating.chlorbenzol sodium nitrate and 66 B. sulf ric acid to a temperature at which nitratin progresses smoothly without evolution ofdarge quan tities of oxids of nitrogen. 7

11. The process of purifying dinitrophenol which comprises adding an alkaline solution thereofto a dilute solution of an acid.

12. The process of making dinitrophenol which comprises nitrating chlorbenzol with sodium nitrate and 66 B. sulfuric acid.

13. Ihe process of nitrating chlorbenzol to form dinitrochlorbenzol which comprises treatin chlorbenzol with a solution formed by mixmg sulfuric acid and. sodium nitrate.

14. Th process of nitrating chlorbenzol to form dinitrochlorbenzol whlch comprises treating chlorbenzol witha solution formed by mixing 66 sulfurioacid and sodium nitrate.

.15. The process of nitrating chlorbenzol to form dinitrochlorbenzol which comprises the sodium nitrate is practically all in soluheating chlorbcnzol 'Withfa solution formed tion, and in reacting with this mixture on If by mixing sulfuric acid and. sodium nitrate approximately one part of monochlorbenzol until the latter is practically all in solution. while heating and agitating; whereby dini- 5 16. The process of making dinitrochlortrochlorbenz'ol is formed in substantial yield. benzol which comprises mixing about two parts of sodium nitrate (crystals) and six CARLETON ELLIS. parts of sulfuric acid and in agitating until ALFRED A. WELLS. 

